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I was taught that the potential decreases in direction of electric field but when we place a positive charge in between it's electric field is too in that same direction but the negative charge has exactly opposite direction of electric field to the parent electric field....so why is it opposite?

Qmechanic
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user93585
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2 Answers2

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why is it opposite?

Physics doesn't really answer the question "why".

We observe that there is a property that some particles have, so that some of them attract each other and some of them repel each other. When two particles have this property in the same way, they repel each other, and when the two particles have the different types of this property they attract each other.

We name this property "charge" and the two types it comes in "positive" and "negative". But giving names to the property doesn't really explain anything about it, it just gives us an easy way to talk about it and remember how it works.

We then create the idea of "electric field" to describe quantitatively how the attraction and repulsion effect changes depending on how the charge is distributed in space. To make the concept of charge consistent with the observation that same charges repel and opposite charges attract, we must have the force from the field on one kind of charge be in one direction and the force on the other kind of charge be in the opposite direction. But again naming the field and writing down equations to describe it doesn't really explain why it exists, or has the effects it has.

The Photon
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I didn't understand your question very clearly. But I'll try to help you best. Because electrons and protons have opposite charge,it is analogous of saying that if an amount of electrons went from A to B, it is the same as protons moving from B to A as the charge changes on the source and end point is same. Apply electric fields to them and probably it is your answer.

Because it was thought earlier (before discovery of electron) that positive charges moved, and we know that flow happens from regions of higher potential to lower potential, protons which move, move from higher potential to lower potential or put in other words in the direction of potential difference. And then to equate or balance the charge change we have to assume negative charges have direction opposite to positive charges.(simple algebra - subtracting is same as adding negative number - removing positive charge is same as adding negative charge and vice versa). And electric field direction is by convention from positive charges to negative charges.

I deleted my previous comments and posted the content in them as an answer.